[PATCH net] net: cls_flower: Remove filter from mask before freeing it

[Petr Machata]

In fl_change(), when adding a new rule (i.e. fold == NULL), a driver may
reject the new rule, for example due to resource exhaustion. By that
point, the new rule was already assigned a mask, and it was added to
that mask's hash table. The clean-up path that's invoked as a result of
the rejection however neglects to undo the hash table addition, and
proceeds to free the new rule, thus leaving a dangling pointer in the
hash table.

Fix by removing fnew from the mask's hash table before it is freed.

Fixes: 35cc3cefc4de ("net/sched: cls_flower: Reject duplicated rules
also under skip_sw")
Signed-off-by: Petr Machata <pe...@mellanox.com>
Acked-by: Jiri Pirko <j...@mellanox.com>
Reviewed-by: Ido Schimmel <ido...@mellanox.com>
---

Notes:
    Note that this is covered by mirror_gre_scale test in
    tools/testing/selftests/drivers/net/mlxsw/spectrum/resource_scale.sh

 net/sched/cls_flower.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index f6aa57fbbbaf..12ca9d13db83 100644
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -1371,7 +1371,7 @@ static int fl_change(struct net *net, struct sk_buff 
*in_skb,
        if (!tc_skip_hw(fnew->flags)) {
                err = fl_hw_replace_filter(tp, fnew, extack);
                if (err)
-                       goto errout_mask;
+                       goto errout_mask_ht;
        }
 
        if (!tc_in_hw(fnew->flags))
@@ -1401,6 +1401,10 @@ static int fl_change(struct net *net, struct sk_buff 
*in_skb,
        kfree(mask);
        return 0;
 
+errout_mask_ht:
+       rhashtable_remove_fast(&fnew->mask->ht, &fnew->ht_node,
+                              fnew->mask->filter_ht_params);
+
 errout_mask:
        fl_mask_put(head, fnew->mask, false);
 
-- 
2.4.11